DEMONSTRATION OF SIMPLE SUBSTANCES
Pupil: What is the problem that we are now to discuss in this book?
Master: Since it is our intention to find the matter and the form in simple substances, and since you question the existence of simple substances, we must first consider—and that is the purpose of this book—the proof of the existence of simple substances. We shall seek assured certainty in this regard to the point of establishing their existence by necessary proofs. Next we shall proceed to an examination of the science of matter and form in simple substances.
Let us begin then by producing the proofs that establish the existence of a substance intermediary between the First Author, sublime and holy, and the substance that supports the nine categories. In this connection we shall postulate the following fundamental principle: If the origin of beings is the First Author, who is not caused, and the end of beings is the final effect, that itself has no effect, then the beginning of things is essentially and actually different from their end. For if the beginning of things is not distinct from their end, then the beginning is the end, and the end is the beginning.
Pupil: What is the nature of the distinction between the First Author, sublime and holy, and the final effect?
Master: By the distinction between them, we understand